Current-rectifying device



Patented June 24, 1930 use,

PATEY wAL'rEn'o. SNELLING, or ALL NrowN, PENNSYLVANIA v CUBRENT-REC'IIFYING DEVICE No Drawing. Original application filed September20y1928, Serial No. 307,846; Divided and this application filed July 31,

My invention relates to currentrcctifying devices of the general nature of natural crystal detectors, and more particularly relates to improvements in contact rectifiers, electric valves, contact detectors, and like def In my pending application S; 307,346,

"filed September 20, 1928, of whichthe 'present application is a division, I have described the preparation of contact rectifying elejments produced by the reduction of a salt of lead by means of an element of the sulfur group. I have discovered, however, that by reducing a salt of lead by a binary compound of sulfur such as hydrogensulfide I can also obtainsimilar contact rectifying bodies, these contact elements having no macroscopic openings or vesicles, but being characterized by the presence of extremely minute openings or pores. By the methods described in my application already referred v to both the composition and the degree of porosity of my products-maybe varied within very wide limits, and products made in accordance with my invention have been found to have important and very valuable properties in the detectionand'modification of electric currents set up as the result of the action of radiantenergy, 7-

7 As an example of my present invention, I will describe a process which I may employ in the preparation of current rectifying agents from lead carbonate. Commercial lead carbonate is first compressed, preferably by means of a hydraulic press into coherent tablets or pellets of desired size and 40 shape. Strong pressure should be used, as lead carbonate tends to produce somewhat friable aggregates unless highly compressed. The pelletsarenext placed in a vessel containing an atmosphere of hydrogen sulfide,

andare heated in this atmosphereofhydrogen sulfide for a total period of from three to five minutes. ,The heating should preferably be'gentle at first, the temperature being graduallyraisedto a dull redhead-LA progressive reaction from the surface of the.

utes theresulting'product will be foundto raw materials, my invention is not strictly 1929. Serial N0. 382,59 r V pellet to its interior goeson, but it is not necessary that the center portion of the pellet should be completely reduced. After a heatingperiod of from three to-five mint,

possess marked current rectifying ability, al-

though both the lead carbonate and the hydrogen sulfide used asraw materials are devoid of current rectifying ability. Y Althou h I have referred specifically to the usefof lead carbonate, either as the pure carbonate or the mixture of lead carbonate and lead hydroxide that is known as comcmercial white lead, as one of my preferred limited to the use of this material, as I have found that other oxygelrcontaining salts of lead such as lead sulfiteand lead thiosulfite may be similarly employed, the significant element of my invention being the dry reductionof an oxygen-containing salt of lead bymeans of a binary compound of an elementof the sulfur group at atemperature above 400 (3.,b11i1 below 1,200- C. I prefer to employ a temperature of6509 (1., corresponding to What is termed a dull red heat, and toemploy a treating period of from one to seven, minutes. When a temper- ,ature in excess of 700- G."is used, I prefer:- to shorten my'treating periodsomewhat, and so whena temperature below 500. C. is employed, I find it desirable to materially lengthen theftreating period beyond the maximum period of seven minutes which gives the .best resultswhenaused within the preferred temperature range. I 7, Q

Although I -obtain, the best results by the use of hydrogen sulfide as they reducing agent which I employin the. dry reduction. of oxygen-containingsalt of lead, my invention is not strictlylimitedto the'employment of hydrogen sulfide, and Irecog- ,mze compoundsof selenium and tellurium porous structure and are not in any way slag-likeor glassy but instead consist of a macroscopically homogeneous but m croscoping elements was unknown, but=by my-prescnt invention I am able to control the sensitiveness of detectors of radiantenergy within wide limits by suitable modifications of the atomic arrangement of my products, the presence of dissolved but probably chemically uncombined metallic oxideand dissolved but probably chemically uncombined non-metallic element having the effect of permitting certain ions to possess a wide freedom of movement within the chemical structure of my'products. Although I do not have suflicient evidence to prove the correctness of my present theory, it is my belief that the extraordinary activity of my present products is due to the presence of dissolved oxide compounds and of a dissolved element of the sulfur group in 'my new compounds, these free or dissolved components so modifying the intermolecular ionic net work which makes up the chemical compound as to leave certain ionsfree to enter into weak combination with one or more of the chemical agents present. When an electric current passes through my new products the conductivity is aidedby the degree of looseness with which these ions are held by the attraction of the dissolved non-metallic element and metal oxide contained in my new compound.

In most of my products a metallic sulfide,

selenide or telluride forms the basic product whose ionic structural net work forms the skeleton of the molecular structure of the material, while a greater or less quantity of metallic oxide and free -non-metallic element provides the source of free or mo bile ions. -Accord-ingly in order to obtain maximum sensitiveness in my products, I find it desirable to avoid such long continued reduction of my oxygen containing component, or such extensive oxidation of my non-metallic component, as will cause the complete elimination of these materials.

By fusing products made in accordance with my lnvention thelr sensitlveness at once decreases to approximately the normal sensi- 'tiveness of the ordinary compound, and the distinctive properties which made my products so desirable become lost.

The use of increased pressure, in the oppartly or wholly eration of making tablets or pellets in accordance with my present invention, leads to increased density of the finished product in all cases. Electrical conductivity is somewhat increased and detecting ability is materially increased by the use of suificient pressure to give a relatively high density to the finished product. It will be evident that in view of the wide variation in the control of conditions which is possible in the practice of my present invention it is not desirable to statetany specific figures for the characteristics of my products, but it is interesting to know that although the specific gravity of lead sulfide as the mineral galena varies from 7 .4 to 7.6, the corresponding product made in accordance with my inpounds of lead,.and also some free or loosely combined sulfur, and accordingly a strict comparison of its specific gravity with the specific gravity of galena is not fair. In general, however, products made in accordance with my invention are less dense than the corresponding minerals which contain the metal and the element of the sulfur group predominating in my product. In appearance my products'are usually smooth, hard blocks, varying in color according to their composition, and even when the surfaces are polished are not glassy or slag-like. My products show no visible openingsexcept on magnification, and are tough and very slightly elastic. i

It will be evident that many modifications may be made without departing from the spirit of my invention as disclosed. Although I haveillustrated my invention by certain specific embodiments, my invention is not limited to the specific illustrations given, but instead possesses exceptionally "wide flexibility inthe preparation ofa new class of bodies having exceptional properties as conductors in electric circuits, and capable of a wide field of application as detectors, rectifiers and amplifiers of electric currents and radiant energy. Accordingly no limitations should be placed upon my' invention, except such as are indicated in the appended claims.

I claim: I

1. The process of preparing current rectifying products which comprises reducing a substantially dry salt of lead by a binary compound of sulfur. 2. The process of preparing current rectifying products which comprises reducing'a substantially dry salt of lead by a'hydrogen compound of an element in the sulfur group 3. The process of preparing current rectifying elements which comprises reducing a substantially dry carbonate of lead by a binary compound of sulfur.

4. The process of preparing current rectifying products which comprlses reducing a substantially dry carbonate of lead by a hydrogen compound of sulfur.

5. The process of preparing current rectitying products which comprises reducing a substantially dry basic lead carbonate by a binary compound of sulfur.

6. The process of preparing. current rectifying products which comprises reducing a substantially dry basic lead carbonate by a hydrogen compound of sulfur.

In testimony whereof,-I have hereunto subscribed my name this 30th day of July,

WALTER O; SNELLING. 

